This invention relates to a single station single satellite offset printing machine for printing both sides of a sheet, in accordance with the independent claims.
Single station single satellite sheet fed printing machines have one common central counter-pressure cylinder around which printing groups are arranged in a xe2x80x9csatellitexe2x80x9d configuration. The common counter-pressure cylinder is therefore the xe2x80x9csunxe2x80x9d of the satellite system. It is conventionally made of thick-walled steel with a hard chromium-plated surface to prevent the ink from offsetting. During printing, 4 colors can be offset or transferred onto one side of the sheet, one immediately after the other, using one single gripper bite during one printing cycle. The gripper system remains closed during the printing process enabling high register precision and a maximum of substrate flexibility.
In conventional offset satellite printing machines (DE 43 03 796 A 1 and U.S. Pat. No. 6,438,352 FIG. 4), the number of rubber and plate cylinder pairs surrounding the common counter pressure cylinder is limited to four for reasons of accessibility to the printing groups and two sequential printing stations must be provided for front and back side printing in two printing cycles, in addition to an intermediate turning or reversing system (see for example U.S. Pat. No. 5,660,108 and DE 43 59 02) and requiring multiple gripper bites (openings and closures). However, multiple gripper bites and/or turning of sheet limit the substrate flexibility and production speed. Prior Art (e.g. U.S. Pat. Nos. 6,438,352 and 5,552,875) also discloses front and back side printing via skipped (interrupted) feeding with the disadvantage of reduced printing speeds.
U.S. Pat. No. 4,493,25 discloses a multi-station printing press in which a plurality of modular printing stations are joined together. Printing on both sides of the sheet requires at least one dual printing station with two blanket carrying cylinders acting, at the same time, as a counter pressure cylinder. During the printing process, the gripper systems open and close during passage through a single station. This multi-station configuration requires an expensive machine with a very large length and height resulting in substantial costs for both for the printing press and the surrounding building. Short setup times are accordingly important. This type of modular configuration is not suited for small runs.
The double sheet fed satellite configuration of U.S. Pat. No. 5,036,763 has multiple counter-pressure cylinders requiring multiple gripper bites. The double satellite arrangement has a very large foot print and is expensive and therefore not suited for small runs and/or for downstream processing.
Due to the requirements of production on demand, 80% of future printing jobs are expected to less than 5000 sheets and will have to be delivered within a few of days, including post-press processing.
In view of this prior art and of future market considerations, it is the underlying object of the invention to introduce a single station single satellite offset printing machine for printing sheets with a maximum of substrate flexibility which enables multiple front side printing and at least a single color back side printing in only one printing cycle without an additional turning, transportation, and/or intermediate drying, which is operable with short setup service times, and which is of compact design, having a minimum number of parts and requiring only modest investment.
The invention achieves this object with a single station single satellite offset printing machine having the features of the independent claims. Other important embodiments of the invention are the subject of the dependent claims.
The inventive single station single satellite printing machine has a single common central counter-pressure cylinder which is structured as a rubber blanket cylinder and which has an associated feed system and a number of at least four to ten satellite printing groups for first side printing disposed, seen in the rotational direction of the common counter-pressure cylinder, between the feed system and the output system and with at least one additional satellite printing group for back side printing disposed, as seen in the rotational direction of the common counter-pressure cylinder, after the output cylinder and before the feed cylinder. This machine design enables multicolor front side printing and at least single-color back side printing on sheet-like printing stock, which can be printed in a single run, without additional gripper bites as are necessary with additional transfer or turning devices. There is only one common counter-pressure cylinder and no need for auxiliary cylinders or a second counter-pressure cylinder. The common counter-pressure cylinder in accordance with the invention is therefore a multiple function cylinder, since it assumes the functions of a counter-pressure cylinder, a rubber blanket cylinder, and a transportation cylinder with gripper systems.
The compact design single station single of the satellite printing machine enables a printing operation even under continuous printing stock feed conditions, which, after the proper feed-in, passes the respective satellite printing groups in accordance with the register setting. Sheet transfer problems and additional gripper functions and feed components are avoided by using only a single gripper bite. For this reason, the inventive satellite printing machine has a high repetition rate for sheet printing and can operate at full printing speed, while enabling high printing quality and rapid setup time. This configuration enables full-size printing of both the front and back side page of the sheet, and only one bordering strip is required for the gripper bite, which cannot be accessed by the printing surface about the plate cylinder. Consequently, waste of paper is considerably reduced. The satellite printing machine with its single gripper bite is particularly suited for printing stock which is difficult to handle, such as card board, multi-layer packaging, etc.
In an advantageous embodiment, each plate and rubber blanket cylinder group of the machine constitutes a cassette-shaped modular unit, which is moveable from an operating position into a service position in a direction towards the operating side or towards the drive side. In spite of the highly packed sequence in which the satellite printing groups are arranged, a quick adjustment to new printing conditions, such as new printing plates, images or rubber blankets, is possible, with good accessibility and simplification of the associated tasks.
Adjustments to the printing groups can be performed in the service position, even while the production processes are running.
The following description and drawings provide additional details and advantageous characteristics of the invention, which are illustrated in an example of the inventive satellite printing machine.